Cimetidine: II. Adverse reactions and patterns of use.

Numerous adverse reactions have been attributed to cimetidine, which is understandable in view of the attention and scrutiny the drug has received, its widespread use, and its systemic effects. The reported frequency of side effects has differed considerably but is surprisingly low in all studies. The drug has caused an array of central nervous system disturbances, gynecomastia, and, rarely, hepatotoxicity, interstitial nephritis, bradycardia, hypotension, and even cardiac arrest. The last complication has occurred with rapid-bolus intravenous injection. Blood dyscrasias have also been rare and usually associated with serious underlying disease or multiple drugs, making it difficult to establish cause and effect in most cases. The drug is used widely to treatment conditions for which it is not approved. Some of these conditions are now believed to respond to cimetidine (gastric ulcer); others are known not to respond (acute upper gastrointestinal bleeding and acute pancreatitis).